Hydrogen Generating Fuel Cell Cartridges

ABSTRACT

A gas-generating apparatus includes a cartridge including a reservoir having a first reactant and a reaction chamber, and a receiver that can include a flow control device. The receiver is adapted to receive the cartridge and to transport the first reactant to the reaction chamber after connection with the cartridge. The flow control device is adapted to stop the transport of reactant when the pressure in the reaction chamber reaches a predetermined pressure.

BACKGROUND OF THE INVENTION

Fuel cells are devices that directly convert chemical energy ofreactants, i.e., fuel and oxidant, into direct current (DC) electricity.For an increasing number of applications, fuel cells are more efficientthan conventional power generation, such as combustion of fossil fuel,as well as portable power storage, such as lithium-ion batteries.

In general, fuel cell technology includes a variety of different fuelcells, such as alkali fuel cells, polymer electrolyte fuel cells,phosphoric acid fuel cells, molten carbonate fuel cells, solid oxidefuel cells and enzyme fuel cells. Today's more important fuel cells canbe divided into several general categories, namely: (i) fuel cellsutilizing compressed hydrogen (H₂) as fuel; (ii) proton exchangemembrane (PEM) fuel cells that use alcohols, e.g., methanol (CH₃OH),metal hydrides, e.g., sodium borohydride (NaBH₄), hydrocarbons, or otherfuels reformed into hydrogen fuel; (iii) PEM fuel cells that can consumenon-hydrogen fuel directly or direct oxidation fuel cells; and (iv)solid oxide fuel cells (SOFC) that directly convert hydrocarbon fuels toelectricity at high temperature.

Compressed hydrogen is generally kept under high pressure and istherefore difficult to handle. Furthermore, large storage tanks aretypically required and cannot be made sufficiently small for consumerelectronic devices. Conventional reformat fuel cells require reformersand other vaporization and auxiliary systems to convert fuels tohydrogen to react with oxidant in the fuel cell. Recent advances makereformer or reformat fuel cells promising for consumer electronicdevices. The most common direct oxidation fuel cells are direct methanolfuel cells or DMFC. Other direct oxidation fuel cells include directethanol fuel cells and direct tetramethyl orthocarbonate fuel cells.DMFC, in which methanol is reacted directly with oxidant in the fuelcell, is the simplest and potentially smallest fuel cell. It also haspromising power application for consumer electronic devices. SOFCconvert hydrocarbon fuels, such as butane, at high heat to produceelectricity. SOFC requires relatively high temperature in the range of1000° C. for the fuel cell reaction to occur.

The chemical reactions that produce electricity are different for eachtype of fuel cell. For DMFC, the chemical-electrical reaction at eachelectrode and the overall reaction for a direct methanol fuel cell aredescribed as follows:

Half-reaction at the anode:

CH₃OH+H₂O→CO₂+6H⁺+6e⁻

Half-reaction at the cathode:

1.5O₂+6H⁺+6e⁻→3H₂O

The overall fuel cell reaction:

CH₃OH+1.5O₂→CO₂+2H₂O

Due to both the migration of the hydrogen ions (H⁺) through the PEM fromthe anode to the cathode and the inability of the free electrons (e⁻) topass through the PEM, the electrons flow through an external circuit,thereby producing an electrical current. The external circuit may beused to power many useful consumer electronic devices, such as mobile orcell phones, calculators, personal digital assistants, laptop computers,and power tools, among others.

DMFC is discussed in U.S. Pat. Nos. 5,992,008 and 5,945,231, which areincorporated herein by reference in their entireties. Generally, the PEMis made from a polymer, such as Nafion® available from DuPont, which isa perfluorinated sulfonic acid polymer having a thickness in the rangeof about 0.05 mm to about 0.5 mm, or other suitable membranes. The anodeis typically made from a Teflonized carbon paper support with a thinlayer of catalyst, such as platinum-ruthenium, deposited thereon. Thecathode is typically a gas diffusion electrode in which platinumparticles are bonded to one side of the membrane.

In another direct oxidation fuel cell, borohydride fuel cell (DBFC)reacts as follows:

Half-reaction at the anode:

BH₄-+8OH—→BO₂-+6H₂O+8e-

Half-reaction at the cathode:

2O₂+4H₂O+8e-→8OH—

In a chemical metal hydride fuel cell, generally aqueous sodiumborohydride is reformed and reacts as follows:

NaBH₄+2H₂O→(heat or catalyst)→4(H₂)+(NaBO₂)

Half-reaction at the anode:

H₂→2H⁺+2e⁻

Half-reaction at the cathode:

2(2H⁻+2e⁻)+O₂→2H₂O

Suitable catalysts for this reaction include platinum and ruthenium, aswell as other metals. The hydrogen fuel produced from reforming sodiumborohydride is reacted in the fuel cell with an oxidant, such as O₂, tocreate electricity (or a flow of electrons) and water byproduct. Asodium borate (NaBO₂) byproduct is also produced by the reformingprocess. A sodium borohydride fuel cell is discussed in U.S. Pat. No.4,261,956, which is incorporated herein by reference. Therefore, theknown chemical hydride reactions that use aqueous metal hydride haveabout 9 to 12 weight percentage storage expectancy, and the liquid andthe catalyst used in the wet chemical reaction system need to be closelymonitored. Additionally, it is difficult to maintain the stability of ametal hydride solution over a long period of time, because according tothe formula t1/2−pH*log(0.034+kT), which provides the half life of thereaction, the reaction of hydrolysis always occurs very slowly.Furthermore, if the solution is stabilized, the reactivity is notcomplete.

In a hydride storage method, the reaction is as follows:

Metal+H₂ hydride+heat

However, storage expectancy of such a reaction is only about 5 weightpercentage. Additionally, such reactions can be expensive and difficultto package.

Another known method to produce hydrogen is a dry hydride reaction. Dryreaction, generally, involves the following reaction:

X(BH₄)→H₂, where X includes, but is not limited to, Na, Mg, Li, etc.

Again, dry reactions have several disadvantages, such as having astorage expectancy of only about 10 weight percentage, and the need toclosely monitor the pressure.

An additional method to produce hydrogen gas is by a pressure storagemethod using the formula PV=nRT, wherein P is pressure, V is volume, nis a number of moles, R is the gas constant, and T is temperature. Thismethod requires constant pressure monitoring.

One of the most important features for fuel cell application is fuelstorage. Another important feature is regulating the transport of fuelout of the fuel cartridge to the fuel cell. To be commercially useful,fuel cells such as DMFC or PEM systems should have the capability ofstoring sufficient fuel to satisfy the consumers' normal usage. Forexample, for mobile or cell phones, for notebook computers, and forpersonal digital assistants (PDAs), fuel cells need to power thesedevices for at least as long as the current batteries and, preferably,much longer. Additionally, the fuel cells should have easily replaceableor refillable fuel tanks to minimize or obviate the need for lengthyrecharges required by today's rechargeable batteries.

One common disadvantage of the known hydrogen gas generators is thatonce the reaction starts, the gas generator cartridge cannot control thereaction. Thus, the reaction will continue until the supply of thereactants run out or the source of the reactant is manually shut down.Moreover, the known hydrogen generators may not work when positioned ina certain orientation and are relatively large in size. Accordingly,there remains a need for improved hydrogen generators and the reactantsproducing hydrogen.

SUMMARY OF THE INVENTION

The present invention relates to a gas-generating apparatus thatincludes at least two separate portions. The first portion of thegas-generating apparatus contains at least a reaction chamber and areactant reservoir. The second portion, which includes a receptacle, isadapted to receive the first portion. The second portion can be part ofa fuel cell or a device that the fuel cell powers. The second portionincludes at least one coupler and/or a flow control device that can becontrolled by the pressure of the reaction chamber or the first portion.When the pressure in the reaction chamber is within a predeterminedlevel, the flow control device closes to stop the transport of the firstreactant to the reaction chamber. One advantage of the present inventionis that when the first portion is separated from the second portion, thereactant cannot be mixed to react with each other.

The present invention also relates to a fuel usable with agas-generating apparatus. The fuel includes a solid metal hydride and anaqueous solution having water, a catalyst, and/or at least one alcoholor a mixture of alcohols. One of the reactants may also include an acidto improve the reaction between the reactants over time.

The present invention also relates to a method for generating gas. It isto be understood that both the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare intended to provide a further explanation of the present invention,as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawing, which forms a part of the specification andis to be read in conjunction therewith and in which like referencenumerals are used to indicate like parts in the various views:

FIG. 1 is a cross-sectional view of a gas-generating apparatus that iscapable of supplying a desired gas to a micro fuel cell.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As illustrated in the accompanying drawing and discussed in detailbelow, the present invention is directed to a fuel supply, which storesfuel cell fuels, such as methanol and water, methanol/water mixture,methanol/water mixtures of varying concentrations, pure methanol, and/ormethyl clathrates described in U.S. Pat. Nos. 5,364,977 and 6,512,005B2, which are incorporated herein by reference in their entirety.Methanol or other alcohols are usable in many types of fuel cells, e.g.,DMFC, enzyme fuel cells and reformat fuel cells, among others. The fuelsupply may contain other types of fuel cell fuels, such as ethanol oralcohols; metal hydrides, such as sodium borohydrides; other chemicalsthat can be reformatted into hydrogen; or other chemicals that mayimprove the performance or efficiency of fuel cells. Fuels also includepotassium hydroxide (KOH) electrolyte, which is usable with metal fuelcells or alkali fuel cells, and can be stored in fuel supplies. Formetal fuel cells, fuel is in the form of fluid borne zinc particlesimmersed in a KOH electrolytic reaction solution, and the anodes withinthe cell cavities are particulate anodes formed of the zinc particles.KOH electrolytic solution is disclosed in United States published patentapplication no. 2003/0077493, entitled “Method of Using Fuel Cell SystemConfigured to Provide Power to One or More Loads,” published on Apr. 24,2003, which is incorporated herein by reference in its entirety. Fuelscan also include a mixture of methanol, hydrogen peroxide and sulfuricacid, which flows past a catalyst formed on silicon chips to create afuel cell reaction. Moreover, fuels include a blend or mixture ofmethanol, sodium borohydride, an electrolyte, and other compounds, suchas those described in U.S. Pat. Nos. 6,554,877; 6,562,497; and6,758,871, which are incorporated by reference in their entireties.Furthermore, fuels include those compositions that are partiallydissolved in a solvent and partially suspended in a solvent, describedin U.S. Pat. No. 6,773,470 and those compositions that include bothliquid fuel and solid fuels, described in United States published patentapplication no. 2002/0076602. These references are also incorporated byreference in their entireties.

Fuels can also include a metal hydride such as sodium borohydride(NaBH₄) and water, discussed above. Fuels can further includehydrocarbon fuels, which include, but are not limited to, butane,kerosene, alcohol, and natural gas, as set forth in United Statespublished patent application no. 2003/0096150, entitled “LiquidHereto-Interface Fuel Cell Device,” published on May 22, 2003, which isincorporated herein by reference in its entirety. Fuels can also includeliquid oxidants that react with fuels. The present invention istherefore not limited to any type of fuels, electrolytic solutions,oxidant solutions or liquids or solids contained in the supply orotherwise used by the fuel cell system. The term “fuel” as used hereinincludes all fuels that can be reacted in fuel cells or in the fuelsupply, and includes, but is not limited to, all of the above suitablefuels, electrolytic solutions, oxidant solutions, gaseous, liquids,solids, and/or chemicals and mixtures thereof.

As used herein, the term “fuel supply” includes, but is not limited to,disposable cartridges, refillable/reusable cartridges, containers,cartridges that reside inside the electronic device, removablecartridges, cartridges that are outside of the electronic device, fueltanks, fuel refilling tanks, other containers that store fuel and thetubings connected to the fuel tanks and containers. While a cartridge isdescribed below in conjunction with the exemplary embodiments of thepresent invention, it is noted that these embodiments are alsoapplicable to other fuel supplies and the present invention is notlimited to any particular type of fuel supply.

The fuel supply of the present invention can also be used to store fuelsthat are not used in fuel cells. These applications can include, but arenot limited to, storing hydrocarbons and hydrogen fuels for microgas-turbine engine built on silicon chips, discussed in “Here Come theMicroengines,” published in The Industrial Physicist (December2001/January 2002) at pp. 20-25. As used in the present application, theterm “fuel cell” can also include microengines. Other applications caninclude storing traditional fuels for internal combustion engines andhydrocarbons, such as butane for pocket and utility lighters and liquidpropane.

Suitable known hydrogen generating apparatus are disclosed in co-pendingU.S. patent application Ser. Nos. 10/679,756 and 10/854,540. Thedisclosures of these references are incorporated herein by reference intheir entireties.

In various embodiments of the present invention, the gas-generatingapparatus of the present invention can function regardless of how it ispositioned, e.g., sideway, diagonal, or upside-down. The gas-generatingapparatus of the present invention, for a small device such as a mobilephone, has a volume of about 100 cm³ or less, preferably about 70 cm³ orless, or about 40 cm³ or less, and includes a cartridge and a receptacle(or receiver). Preferably, the cartridge or a portion thereof isdisposable and contains the reactive compositions. The receiver caninclude flow control device, conduits, pathways, or channels adapted totransport the reactive compositions in the cartridge to come in contactand react with one another. Preferably, the receiver is removablyattachable from the cartridge. The reactive compositions in thecartridge cannot contact each other unless the cartridge has beenconnected to the receiver. The receiver can also direct the generatedgas towards the fuel cell.

The cartridge includes a reservoir having a first reactant and areaction chamber. The reaction chamber can include a second reactant.The first reactant can include water and the second reactant can includea metal hydride, e.g., sodium borohydride. The reactants can be ingaseous, liquid, or solid form. Preferably, the first reactant is waterthat can optionally include an additive and/or a catalyst. The secondreactant is preferably a solid metal hydride or a solid metalborohydride. The solid reactants can be powder, pellets, porousstructures, balls, tubes, soluble sheaths or can be deposited on thewalls of the reaction chamber, among other forms. The reaction of waterand metal hydride can produce hydrogen gas. Other suitable reactants orreagents are disclosed in U.S. patent application Ser. No. 10/854,540,which is previously incorporated herein. Additionally, the firstreactant can be methanol or a hydrocarbon, such as butane, and thereaction chamber contains one or more catalyst or is capable ofgenerating heat, and no reactant. The first reactant may be hydrolyzedin the presence of the catalyst(s) or heat in the reaction chamber.

The receiver or receptacle of the present invention is capable oftransporting a first reactant from a reservoir in the cartridge to areaction chamber in the cartridge. The pressure inside the reactionchamber can control the transport of the first reactant from thereservoir into the reaction chamber. For example, the first reactant inthe reservoir can be introduced into the reaction chamber when thepressure inside the reaction chamber is less than a predetermined value,or alternatively, if the pressure inside the reaction chamber is lessthan the pressure in the reservoir by a predetermined amount. The flowof the first reactant from the reservoir into the reaction chamber ispreferably self-regulated. Thus, when the reaction chamber reaches apredetermined pressure or above the pressure in the reservoir, the flowof the first reactant from the reservoir into the reaction chamber canbe stopped to prevent further production of hydrogen gas. Similarly,when the pressure of the reaction chamber is reduced below thepredetermined value or below the pressure in the reservoir by apredetermined amount, the first reactant again flows from the reservoirinto the reaction chamber. The first reactant in the reservoir can beintroduced into the reaction chamber by any known method including, butnot limited to, pumping, osmosis, capillary action, pressuredifferential, valve, or one or more combinations thereof. Preferably,the reservoir is pressurized to provide the energy to transport thefirst reactant to the reaction chamber. The pressure in the reservoir iscreated by a pressure applicator, such as a spring, foam piston,propellant gas, liquefied hydrocarbon, and/or deformable flexible walls.

Cartridge 10 of the present invention includes reservoir 12, whichcontains first reactant 14 and reaction chamber 18, which containsoptional second reactant 20. In one exemplary embodiment (not shown inFIG. 1), reservoir 12 can include a bladder or liner holding firstreactant 14. When a bladder is used, the bladder can be made from anymaterial, including flexible material or elastic material.

As illustrated in FIG. 1, gas-generating apparatus 1 includes acartridge 10 and receiver 30. In one example, cartridge 10 and receiver30 are removably connectable to one another by one or more couplers. Forexample, cartridge 10 can be removably connected to receiver 30 by threevalve components 24 and three valve components 32. Suitable couplers 24and 32 include, but are not limited to, car-sealing quick actioncouplers, check valves, duckbill valves, solenoid valves, needle andseptum, electrical valves, and magnetic valves. Other suitable valvesinclude those disclosed in U.S. patent application Ser. Nos. 10/629,006and 10/978,949, which are incorporated by reference herein in theirentireties. However, any known couplers to one skilled in the art can beused to connect cartridge 10 to receiver 30. Couplers 24 and 32 can alsoact as part of, or as extension of, conduits 34 and 38, which are usedto transport first reactant 14 and the generated gas, respectively. Whencartridge 10 is connected to receiver 30, couplers 24 a, 24 b, and 24 cextend from cartridge 10 and are connected to corresponding couplers 32a, 32 b, and 32 c, respectively. As shown, first reactant 14 istransportable from reservoir 12 through couplers 24 a, 32 a throughconduit 34 a and valve 36 and is then returnable to reaction chamber 18of cartridge 10 through conduit 34 b and couplers 32 b, 24 b. Eachcoupler or valve component 24, 32, preferably has internal seal toprevent reactants from leaking when cartridge 10 is separated fromreceptacle 30. An advantage of the present invention is that the firstand second reactants do not contact each other until cartridge 10 isinserted into receiver 30.

Reservoir 12 is preferably pressurized, for example, by a pressureapplicator 16 capable of applying a predetermined amount of pressure toreservoir 12 or the bladder containing first reactant 14. Some exemplarypressure applicators include, but are not limited to, spring, foam,piston, propellant gas, liquefied hydrocarbon, deformable flexiblewalls, or a combination thereof. As shown, a compressed spring 17 ispushing a movable wall 19 to apply pressure on reservoir 12. Movablewall 19 may form a seal with the inner wall of reservoir 12. Otherdevices capable of generating a force and/or applying pressure known toone skilled in the art can also be used in the present invention as thepressure applicator.

Reaction chamber 18, in addition to storing second reactant 20, may alsoinclude a liquid impermeable/gas permeable member 22 that allows thegenerated hydrogen gas to exit reaction chamber 18, and at the same timeto keep liquid reactants within reaction chamber 18. Preferably, gaspermeable member 22 is connected to coupler 24 c that is incommunication with coupler 32 c and conduit 38. Gas permeable member 22can be made of any liquid impermeable/gas permeable material known toone skilled in the art. Such materials can include, but are not limitedto, hydrophobic materials having an alkane group. More specific examplesinclude, but are not limited to: polyethylene compositions,polytetrafluoroethylene, polypropylene, polyglactin (VICRY®),lyophilized dura mater, or a combination thereof. Gas permeable member22 may comprise a gas permeable/liquid impermeable membrane covering aporous member. Examples of such membrane are CELGARD® and GORE-TEX®.Other gas permeable, liquid impermeable members usable in the presentinvention include, but are not limited to, SURBENT® PolyvinylideneFluoride (PVDF) having a porous size of from about 0.1 μm to about 0.45μm, available from Millipore Corporation. The pore size of SURBENT® PVDFregulates the amount of water and/or methanol exiting the system.Materials such as electronic vent type material having 0.2 μm hydro,available from W.L. Gore, can also be used in the present invention.Additionally, 0.25 inch diameter rods having a pore size of about 10 μm,2 inch diameter discs with a thickness of about 0.3 μm, from GenPore,and sintered and/or ceramic porous material having a pore size of lessthan about 10 μm from Applied Porous Technologies Inc. are also usablein the present invention. Furthermore, nanograss materials, from BellLabs, are also usable to filter the liquid. Nanograss controls thebehavior of tiny liquid droplets by applying electrical charges tospecially engineered silicon surfaces that resemble blades of grass.Additionally, or alternatively, the gas permeable, liquid impermeablematerials disclosed in U.S. patent application Ser. No. 10/356,793 arealso usable in the present invention, all of which are incorporatedherein by reference in their entirety.

Receiver 30 of the present invention includes a valve or a flow controldevice 36 connected to conduits 34 a and 34 b, as shown. Flow controldevice 36 can be any device that allows first reactant 14 to enterreaction chamber 18 under predetermined conditions. Some examples offlow control device 36 are: a check valve, a duckbill valve, a solenoidvalve, a magnetic valve, and other mechanical and electrical valves. Inthis embodiment, when the pressure in reaction chamber 18 and reservoir12 are within a predetermined difference, e.g., X psi, flow controldevice 36 can remain closed so that no flow of first reactant 14 occurs.Hence, gas-generating apparatus 1 is in the non-operative state or “OFF”position when reaction chamber 18 is pressurized. In one example, X isabout 2 psi, however, X can be any pressure. When hydrogen is needed,valve 40 opens and the pressure in reaction chamber 18 is drawn down.When the pressure in reaction chamber 18 is less than X psi from thepressure in reservoir 12, and flow control device 36 opens, firstreactant 14 is transported from reservoir 12 through couplers 24 a, 32a, and through conduit 34 a, flow control device 36, conduit 34 b, andcouplers 32 b, 24 b to reaction chamber 18. There, first reactant 14reacts with second reactant 20 (or heated or exposed to catalysts) toproduce hydrogen. The produced hydrogen permeates through gas permeablemember 22 and exits from cartridge 10 through couplers 24 c, 32 c, andfrom receiver 30 through conduit 38 and through shut-off valve 40 to afuel cell.

Prior to the first use, reaction chamber 18 can also include an inertgas. The inert gas is pressurized, e.g., pre-loaded, to a levelapproaching the predetermined pressure that closes valve 36 to stop theflow of first reactant 14 from reservoir 12 into reaction chamber 18.After cartridge 10 is connected for the first time to receiver 30, thepressurized gas prevents the opening of valve 36, thereby preventing thetransport of first reactant 14 to start the reaction. When production ofhydrogen is required, shut-off valve 40 is opened to release the inertgas and draw down the pressure in reaction chamber 18. Hence, valve 36opens to start the flow of first reactant 14 to produce hydrogen.Alternatively, the inert gas can be replaced by hydrogen so that thepreloading gas can be consumed by the fuel cell.

When hydrogen gas is needed, shut-off valve 40 opens and gas producingapparatus 1 is in the operative or “ON” position. As the inert gas orhydrogen is transported out of reaction chamber 18, the pressure withinreaction chamber 18 decreases and the pressure difference betweenreservoir 12 and reaction chamber 18 exceeds X psi. This difference inpressure opens flow control device 36, and first reactant 14 is pushedby spring 17 through flow control device 36 to react with secondreactant 20 in reaction chamber 18. The reaction between first reactant14 and second reactant 20 generates hydrogen gas, which is separatedfrom the liquid inside reaction chamber 18 via gas permeable member 22.The separated hydrogen gas can then reach the fuel cell via conduit 38and shut-off valve 40.

When the generated hydrogen gas is no longer in demand and shut-offvalve 40 is closed, reaction chamber 18 re-pressurizes (since firstreactant 14 and second reactant 20 continue to mix until flow controldevice 36 closes). Once the pressure has reached the predeterminedlevel, flow control device 36 closes to stop the flow of first reactant14 into reaction chamber 18. The cycle can restart again when hydrogengas is needed.

When the rate of hydrogen production exceeds the rate of hydrogenwithdrawal from the cartridge, the pressure in reaction chamber 18gradually increases causing valve 36 to shut down to stop the transportof first reactant 14. When the rate of withdrawal catches up, thepressure in reaction chamber 18 decreases causing valve 36 to open torestart the production of hydrogen. This cycle automaticallyself-regulates during the life of the cartridge.

Pressure applicator 16 may be spring 17 or can include liquefiedhydrocarbons, such as N-butane, isobutane, or a mixture of isobutane andpropane. The liquid gas phase diagram of these materials is such that aslong as some of the hydrocarbon remains in liquid form, its pressure isconstant at constant temperature. In one example, the pressure withinreservoir 12 is maintained at 17 psi (with N-butane, at roomtemperature).

In some exemplary embodiments, first reactant 14 and/or second reactant20 can include at least one of an optional catalyst, a hydrogen-bearingfuel, an agent, wherein the agent can be a second hydrogen-bearing fuelthat can react with the first hydrogen-bearing fuel in the presence orabsence of the catalyst to produce a gas, and optionally an additive.Preferably, the agent reacts with the hydrogen-bearing fuel in thepresence of a catalyst to generate the desired gas. Preferably, firstreactant 14 in reservoir 12 or the bladder and second reactant 20 inreaction chamber 18 do not have the same composition. Moreover,hydrogen-bearing fuel and the agent are in separate chambers. Morepreferably, first reactant 14 includes the agent, such as water whichalso contains hydrogen, and second reactant 20 includes thehydrogen-bearing fuel, such as a metal borohydride or a metal hydride.

The hydrogen-bearing fuel of the present invention can be any fuelcapable of producing hydrogen, when reacted with an agent/compositionand/or placed under certain conditions. In some exemplary embodiments,the hydrogen-bearing fuel can include a metal hydride capable ofreleasing hydrogen upon contact with an agent, which can be anotherhydrogen-bearing fuel, such as water. The reaction between the metalhydride and water can be described as:

MH_(x)+2H₂O→M(OH)₄+xH₂

Examples of the fuel can include, but are not limited to, hydrides ofelements of Groups IA-IVA of the Periodic Table of the Elements andmixtures thereof, such as alkaline or alkali metal hydrides, or mixturesthereof. Other compounds, such as alkali metal-aluminum hydrides(alanates) and alkali metal borohydrides may also be employed. Morespecific examples of metal hydrides include, but are not limited to,lithium hydride, lithium aluminum hydride, lithium borohydride, sodiumhydride, sodium borohydride, potassium hydride, potassium borohydride,magnesium hydride, calcium hydride, and salts and/or derivativesthereof. The preferred hydrides are sodium borohydride, magnesiumborohydride, lithium borohydride, and potassium borohydride. Preferably,the hydrogen-bearing fuel comprises the solid form of NaBH₄ or Mg(BH₄)₂.In solid form, NaBH₄ does not hydrolyze in the absence of water andtherefore improves shelf life of the cartridge. However, the aqueousform of hydrogen-bearing fuel, such as aqueous NaBH₄, can also beutilized in the present invention. When an aqueous form of NaBH₄ isutilized, the chamber containing the aqueous NaBH₄ also includes astabilizer. Exemplary stabilizers can include, but are not limited to,metals and metal hydroxides, such as alkali metal hydroxides. Examplesof such stabilizers are described in U.S. Pat. No. 6,683,025, which isincorporated herein by reference in its entirety. Preferably, thestabilizer is NaOH.

As stated above, the solid form of the hydrogen-bearing fuel ispreferred over the liquid form. In general, solid fuels are moreadvantageous than liquid fuels because the liquid fuels containproportionally less energy than the solid fuels and the liquid fuels areless stable than the counterpart solid fuels.

First reactant 14 can comprise an agent that is capable of reacting withthe hydrogen-bearing fuel in the presence of an optional catalyst togenerate hydrogen. The agent can be a compound or a composition that canact as a source of proton. Some exemplary sources of proton include, butare not limited to, water, alcohols, and/or dilute acids. The mostcommon source of proton is water. As indicated above and in theformulation below, water can react with a hydrogen-bearing fuel, such asNaBH₄ in the presence of an optional catalyst to generate hydrogen.

X(BH₄)_(y)+2H₂O→X(BO)₂+4H₂

Where X includes, but is not limited to, Na, Mg, Li and all alkalinemetals, and Y is an integer.

First reactant 14 can also include optional additives that reduce orincrease the pH of the solution. The pH of first reactant 14 candetermine the speed at which hydrogen is produced. For example,additives that reduce the pH of first reactant 14 result in a higherrate of hydrogen generation. Such additives include, but are not limitedto, acids, such as acetic acid. Conversely, additives that raise the pHcan lower the reaction rate to the point where almost no hydrogenevolves. The solution of the present invention can have any pH valueless than 7, such as a pH of from about 1 to about 6 and, preferably,from about 3 to about 5.

In some exemplary embodiments, the first reactant, the second reactant,or both can include a catalyst that can initiate and/or facilitate theproduction of hydrogen gas by increasing the rate at which firstreactant 14 reacts with second reactant 18. The catalyst of the presentinvention can include any shape or size that is capable of promoting thedesired reaction. For example, the catalyst can be small enough to forma powder or it can be as large as reservoir 12 or reaction chamber 18.In some exemplary embodiments, the catalyst is a catalyst bed. Thecatalyst can be located inside reservoir 12 or the bladder (if any),reaction chamber 18, proximate to reservoir 12, and/or proximate toreaction chamber 18, as long as at least one of either first reactant 14or second reactant 20 can come into contact with the catalyst.

The catalyst of the present invention can include one or moretransitional metals from Group VIIIB of the Periodic Table of theElements. For example, the catalyst can include transitional metals suchas iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh),platinum (Pt), palladium (Pd), osmium (Os), iridium (Ir). Additionally,transitional metals in Group IB, i.e., copper (Cu), silver (Ag), andgold (Au), and in Group IIB, i.e., zinc (Zn), cadmium (Cd), and mercury(Hg), can also be used in the catalyst of the present invention. Othertransitional metals that can be used as part of a catalyst include, butare not limited to, scandium (Sc), titanium (Ti), vanadium (V), chromium(Cr), and manganese (Mn). Transition metal catalysts useful in thecatalyst systems of the present invention are described in U.S. Pat. No.5,804,329, which is incorporated herein by reference in its entirety.The preferred catalyst of the present invention is CoCl₂.

Some of the catalysts of the present invention can generically bedefined by the following formula:

M_(a)X_(b)

wherein M is the cation of the transition metal, X is the anion, and “a”and “b” are integers from 1 to 6 that are needed to balance the chargesof the transition metal complex.

Suitable cations of the transitional metals include, but are not limitedto, iron (II) (Fe² ⁻) iron (III) (Fe³⁺), cobalt (Co²⁺), nickel (II)(Ni²⁺), nickel (III) (Ni³⁺), ruthenium (III) (Ru³⁺), ruthenium (IV)(Ru⁴⁺), ruthenium (V) (Ru⁵⁺), ruthenium (VI) (Ru⁶⁺), ruthenium (VIII)(Ru⁸⁺), rhodium (III) (Rh³⁺), rhodium (IV) (Rh⁴⁺), rhodium (VI) (Rh⁶⁺),palladium (Pd²⁺), osmium (III) (Os³⁺), osmium (IV) (Os⁴⁺), osmium (V)(Os⁵⁺), osmium (VI) (Os⁶⁺), osmium (VIII) (Os⁸⁺), iridium (III) (Ir³⁺),iridium (IV) (Ir⁴⁺), iridium (VI) (Ir⁶⁺), platinum (II) (Pt²⁺), platinum(III) (Pt³⁺), platinum (IV) (Pt⁴⁺), platinum (VI) (Pt⁶⁺), copper (I)(Cu⁺), copper (II) (Cu²⁺), silver (I) (Ag⁺), silver (II) (Ag²⁺), gold(I) (Au⁺), gold (III) (Au³⁺), zinc (Zn²⁺), cadmium (Cd²⁺), mercury (I)(Hg⁺), mercury (II) (Hg²⁺), and the like.

Suitable anions include, but are not limited to, hydride (H⁻), fluoride(F⁻), chloride (Cl⁻), bromide (Br⁻), iodide (I⁻), oxide (O²⁻), sulfide(S²⁻), nitride (N³⁻), phosphide (P⁴⁻), hypochlorite (ClO⁻), chlorite(ClO²⁻), chlorate (ClO³⁻), perchlorate (ClO⁴⁻), sulfite (SO₃ ²⁻),sulfate (SO₄ ²⁻), hydrogen sulfate (HSO⁴⁻), hydroxide (OH⁻), cyanide(CN⁻), thiocyanate (SCN⁻), cyanate (OCN⁻), peroxide (O₂ ²⁻), manganate(MnO₄ ²⁻), permanganate (MnO⁴⁻), dichromate (Cr₂O₇ ²⁻), carbonate (CO₃²⁻), hydrogen carbonate (HCO₃ ⁻), phosphate (PO₄ ²⁻), hydrogen phosphate(HPO₄ ⁻), dihydrogen phosphate (H₂PO₄ ⁻), aluminate (Al₂O₄ ²⁻), arsenate(AsO₄ ³⁻), nitrate (NO₃ ⁻), acetate (CH₃COO⁻), oxalate (C₂O₄ ²⁻), andthe like. A preferred catalyst is cobalt chloride.

In some exemplary embodiments, the optional additive, which can be inreservoir 12 and/or in reaction chamber 18, can be any composition thatis capable of substantially preventing the freezing of or reducing thefreezing point of first reactant 14 and/or second reactant 20. In someexemplary embodiments, the additive can be an alcohol-based composition,such as an anti-freezing agent. Preferably, the additive of the presentinvention is CH₃OH. However, as stated above, any additive capable ofreducing the freezing point of first reactant 12 and/or second reactant20 can be used.

Preferably, the fuel for a hydrogen-generating system of the presentinvention includes a solid metal hydride, and an aqueous solution havingwater, a catalyst, such as CoCl₂, and an alcohol, such as CH₃OH. Morepreferably, the aqueous solution optionally includes an acid having a pHof from about 3 to 5. An example of an acid that is added to the aqueoussolution is acetic acid. One purpose of the acid in the presentinvention is to allow a more constant reaction between the aqueoussolution and the solid fuel by preventing the formation of a barrier atthe entrance of reaction chamber 12.

In the above described embodiment, the pressurization of reactionchamber 18 caused by the production of hydrogen, when demand forhydrogen is ceased, closes flow control device 36 to stop the transportof first reactant 14 in reservoir 12, which in turn stops the reactionthat produces more hydrogen.

Some exemplary formulations of the present invention are summarized inTable I.

TABLE I Formulation of Reactants inside Cartridge 10 Watt- Hour WeightVolume Cartridges (%) (%) Example 1 NaBH₄ 47.36 48.09 CoCl₂ * 2.09 1.06CH₃OH 6.28 7.72 H₂O 44.27 43.12 * CoCl₂ is in a 6 molar water solution.

Based on the above exemplary formulation, suitable fuels may containsolid metal hydride in an amount of from about 42 to about 52 weightpercentage, water in an amount of from about 40 to about 50 weightpercentage, catalyst in an amount of from about 0.1 to about 4 weightpercentage, and alcohol is in an amount of from about 1 to about 10weight percentage. Expressed differently, suitable fuels may containsolid metal hydride in an amount of from about 43 to about 53 volumepercentage, water in an amount of from about 39 to about 49 volumepercentage, catalyst in an amount of from about 0.1 to about 3 volumepercentage, and alcohol in an amount of from about 3 to about 11 volumepercentage.

The exemplary fuel exhibits improved hydrogen storage of up to about 9percent by weight or more.

Other embodiments of the present invention will be apparent to thoseskilled in the art from consideration of the present specification andpractice of the present invention disclosed herein. It is intended thatthe present specification and examples be considered as exemplary onlywith a true scope and spirit of the invention being indicated by thefollowing claims and equivalents thereof.

1-36. (canceled)
 37. A fuel for a hydrogen-generating system comprising:a solid metal hydride; and an aqueous solution comprising water, acatalyst, and an alcohol.
 38. The fuel of claim 37, wherein the metalhydride comprises of sodium borohydride, lithium borohydride, andpotassium borohydride.
 39. The fuel of claim 37, wherein the aqueoussolution has a pH of from about 2 to about
 7. 40. The fuel of claim 37,wherein the aqueous solution comprises acetic acid.
 41. The fuel ofclaim 37, wherein the catalyst comprises of iron, cobalt, nickel,ruthenium, rhodium, palladium, osmium, iridium, platinum, copper,silver, gold, zinc, cadmium, and mercury.
 42. The fuel of claim 37,wherein the catalyst comprises a cation of a transition metal, andanion.
 43. The fuel of claim 42, wherein the cation comprises of iron(II), iron (III), cobalt, nickel (II), nickel (III), ruthenium (III),ruthenium (IV), ruthenium (V), ruthenium (VI), ruthenium (VIII), rhodium(III), rhodium (IV), rhodium (VI), palladium, osmium (III), osmium (IV),osmium (V), osmium (VI), osmium (VIII), iridium (III), iridium (IV),iridium (VI), platinum (II), platinum (III), platinum (IV), platinum(VI), copper (I), copper (II), silver (I), silver (II), gold (I), gold(III), zinc, cadmium, mercury (I) and mercury (II).
 44. The fuel ofclaim 42, wherein the anion comprises of , hydride, fluoride, chloride,bromide, iodide, oxide, sulfide, nitride, phosphide, hypochlorite,chlorite, chlorate, perchlorate, sulfite, sulfate, hydrogen sulfate,hydroxide, cyanide, thiocyanate, cyanate, peroxide, manganate,permanganate, dichromate, carbonate, hydrogen carbonate, phosphate,hydrogen phosphate, dihydrogen phosphate, aluminate, arsenate, nitrate,acetate, and oxalate.
 45. The fuel of claim 37, wherein the alcoholcomprises of methanol, ethanol, isopropanol, n-butanol, t-butanol,ethyleneglycol, or a combination thereof.
 46. The fuel of claim 37,wherein the solid metal hydride is in an amount of from about 42 toabout 52 weight percentage, wherein the water is in an amount of fromabout 40 to about 50 weight percentage, wherein the catalyst is in anamount of from about 0.1 to about 4 weight percentage, and wherein thealcohol is in an amount of from about 1 to about 10 weight percentage.47. The fuel of claim 46, wherein the metal hydride is NaBH₄, thecatalyst is CoCl₂, and the alcohol is CH₂OH.
 48. The fuel of claim 37,wherein the solid metal hydride is in an amount of from about 43 toabout 53 volume percentage, wherein the water is in an amount of fromabout 39 to about 49 volume percentage, wherein the catalyst is in anamount of from about 0.1 to about 3 volume percentage, and wherein thealcohol is in an amount of from about 3 to about 11 volume percentage.49. The fuel of claim 48, wherein the metal hydride is NaBH₄, thecatalyst is CoCl₂, and the alcohol is CH₂OH. 50-57. (canceled)